White Paper- Vapor Barriers (Retarders) and Air Barriers

Air and moisture can get into a home a number of ways. Convective transfer involves moving air, such as a draft around a window or door, electrical boxes, or other wall penetrations. Diffusion refers to moisture moving through a material, similar to a sponge soaking up water. Cavity wall construction typically with fiberglass batt placed into the cavities between studs allows air to pass through and requires an additional, separate vapor barrier, typically polyethylene sheet (Visqueen) or kraft paper facing on the fiberglass batts. Continuous insulation (EPS foam or XPS foam) can also be used as a vapor barrier. Vapor